Precipitation polymerization process for producing an oil adsorbent polymer capable of entrapping solid particles and liquids and the product thereof

ABSTRACT

A process for producing a microporous oil sorbent polymer comprising the steps of: 
     dissolving a polyunsaturated monomer in a silicone organic solvent to provide a monomer mixture containing more than 90% by weight polyunsaturated monomer; 
     polymerizing said monomers by precipitation polymerization, under an inert atmosphere to precipitate microporous, micro-particles in the form of micro-particles, agglomerates and aggregates having a bulk density of about 0.02 gm/cm 3  to about 0.1 gm/cm 3  and capable of adsorbing at least about 20% by weight organic materials based on the total weight of polymer plus adsorbed organic material.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.08/486,107 filed Jun. 7, 1995 abandoned, and application Ser. No.08/486,455 filed Jun. 7, 1995 now U.S. Pat. No. 5,618,877 which is acontinuation-in-part of application Ser. No. 08/327,580 filed Oct. 24,1994, abandoned.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to a precipitation polymerization processfor producing an oil adsorbent polymer in the form of unitmicro-particles, aggregates and agglomerates of micro-particles capableof entrapping any desired oleophilic solid and/or oleophilic liquidcompound for delivery. More particularly, the present invention relatesto a process for producing a highly porous and highly cross-linkedpleophilic polymer in the form of individual micro-particles; aggregatesof micro-particles; and clusters of aggregates (agglomerates) ofmicro-particle spheres characterized by a unit particle size of about0.1 to about 100 microns, preferably about 0.1 to about 80 microns,preferably having a mean particle size of about 5 to about 12 micronsand an oil sorbency of at least about 80% by weight or greater, based onthe weight of adsorbed oil plus micro-particle adsorbent polymer. Thepresent invention is also directed to the assemblies of oil adsorbentmicro-particle aggregates produced by the process having sizes up toabout 3000 microns preferably less than about 1000 microns. Themicro-particles produced by the process of the present invention haveextremely low apparent bulk densities in the range of about 0.02 gm/ccto about 0.1 gm/cc, preferablyabout 0.03 gm/cc to about 0.07 gm/cc, morepreferably about 0.03 gm/cc to about 0.04-0.05 gm/cc. Themicro-particles produced by the process of the present invention arecapable of holding and releasing oleophilic oils, creams, cleaners,medicaments and other organic active compounds and compositions, for usein the cosmetic, cleaning, chemical process and pharmaceuticalindustries.

B. Background

Early disclosures of polymer particles appear in U.S. Pat. Nos.3,493,500 and 3,658,772, which issued on Feb. 3, 1970 and Apr. 25, 1972,respectively. They teach the production of aqueous suspensions ofpolymer particles from acrylic acid monomer and/or acrylamide monomer inan aqueous reaction medium at pH 1-4. Both patents teach that theresultant polymer suspensions, which were not characterized as toparticle size or structure, were suitable for use as flocculating agentsfor sewage treatment.

It was subsequently discovered that polymers could be made in a porousparticulate form by a variety of techniques. The art has stated that"the type of polymerization technique used is an important factor in thedetermination of the resulting product." See U.S. Pat. No. 4,962,170 atcolumn 2, line. 4. As stated in the '170 patent at column 2, lines 7-11,"within each type of polymerization, there are procedural alternativeswhich can have significant impact on the resulting product" " t!hedifferences in the polymerization techniques are enough that a procedureused in one type of polymerization technique that will not necessarilyhave the same effect if used in another polymerization technique." Thus,there is a significant degree of unpredictability in the art.

Porous polymeric particles are capable of being prepared by one of twoprocesses--precipitation polymerization in a single solvent system, orsuspension polymerization in a two phase liquid system. Theprecipitation polymerization technique is presented in U.S. Pat. Nos.4,962,170 and 4,962,133 both of which issued on Oct. 9, 1990. The '170patent discloses a precipitation polymerization process wherein thedisclosed monomers are soluble in the single solvent system, whereas theresulting polymer, which is insoluble, precipitates out of solution oncea critical size is obtained. In the '170 process, the solution ofmonomer consists exclusively of one or more types of polyunsaturatedmonomer. Because each monomer is polyunsaturated, each monomer alsofunctions as a cross-linker, resulting in a highly cross-linked polymerparticle.

Like the '170 patent, the '133 patent also utilizes the precipitationpolymerization process for producing a porous polymeric particle.However, unlike the '170 process, wherein the monomer solution consistsexclusively of polyunsaturated monomers, the '133 process discloses themonomer solution may include one monosaturated monomer in combinationwith one polyunsaturated monomer, wherein the polyunsaturated monomermay comprise up to 90% by weight of the total weight of monomers.Because the precipitation polymerization technique relies upon theformation of polymer aggregates of precipitated polymer particles, themonomer solution is not vigorously agitated during polymerization toavoid separation of the aggregated polymer particles.

U.S. Pat. No. 5,316,774 is directed to a suspension polymerizationprocess, again limited to a maximum of 90% by weight polyunsaturatedmonomers based on the total weight of monomers. Accordingly, it is anobject of the present invention to provide a process for making sorbentmicropolymers from a monomer solution that contains more than 90% byweight, preferably about 92% to 100% polyunsaturated monomers, by weightbased on the total weight of monomers in the monomer solution.

The '133 process is limited to a solvent system that is anaqueous/organic azeotrope. Because the organic solvent cannot beseparated from the water in an azeotrope, azeotropic solutions presentspecial waste disposal problems. Accordingly, it is an object of thepresent invention to provide a process for making oil adsorbentmicropolymers that does not require an azeotropic solution. Further, theparticles produced by the '133 process range extensively in size fromless than about 1 micron in average diameter for unit particles to abouttwelve hundred microns in average diameter for clusters of fusedaggregates. The large variability in size limits the utility andproperties of the polymeric particles. Accordingly, it is also an objectof the present invention to provide a process for making polymericmicro-particles of a less diverse size distribution.

Another process disclosed in the art for producing microscopic polymersis in situ suspension polymerization wherein an active ingredientincluded within the monomer mixture is retained in the formed polymerupon completion of polymerization. Examples of in situ suspensionpolymerization include U.S. Pat. No. 4,724,240 wherein polymerization ofa monounsaturated monomer and a polyunsaturated monomer in anaqueous/polyvinylpyrrolidone system containing an emollient, as theactive agent, produced only relatively large micro-particles, having amean diameter "between 0.25 to 0.5 mm" (250 to 500 microns) thatcontains the emollient therein upon completion of polymerization. Aproblem with a particle having a mean diameter of 250-500 microns isthat the particle is capable of being sensed by touch. This is anundesirable property if the particle is to be used in a lotion or creamor other cosmetic formulations. Accordingly, it is also an object of thepresent invention to provide a process that is capable of manufacturingpolymeric particles having a smaller mean diameter, e.g., 0.5 μm to 120μm, for a smoother skin feel; as well as aggregates and assemblies ofaggregates capable of entrapping oleophilic solids and viscous liquids.

A second problem with the process of the '240 patent is that it islimited to those active ingredients that are capable of dissolving inthe organic solvent. The polymeric micro-particles of the presentinvention are capable of adsorbing organic compounds and organiccompositions containing hydrophobic compounds dissolved in an organicsolvent, as well as solid organic compounds entrapped within an interiorof an open center of an aggregated cluster of micro-particle spheres.Further, the active ingredient(s), which may be proprietary, must beprovided in bulk to the polymer manufacturer so that they may becometrapped in the particles during the polymerization process. To overcomethese problems, it is a further object of the present invention toprovide polymeric micro-particle aggregates having an evacuated internalvolume, defined within a continuous string or cluster of aggregatedmicro-particle spheres, that are capable of adsorbing and entrappinghydrophobic solids and fluids, within the interior surface area of eachopen sphere, in large amounts so that they may be loaded within theinterior volume surrounded by the micro-particle spheres with adsorbedactive hydrophobic organic ingredient(s) in solid or solvent-dissolvedform, and loaded on the exterior surface area of the aggregated sphereswith any hydrophilic compound, in solid form or as an organicsolvent-based viscous solution or dispersion.

A third problem with the '240 process is that it is not suited for usewhen the active ingredient is a mixture of components that differsignificantly from one another as to lipophilicity. In such a situation,the more lipophilic of the active ingredients would be selectivelyisolated in the pores of the polymer made by the '240 process. Toovercome this problem, the '240 process would have to be separatelyapplied to each of the active ingredients, and thereafter, the resultingproducts would be mixed. However, such additional processing and mixingis costly. Accordingly, it is a further object of the present inventionto provide a process for producing a aggregates of micro-particleswherein the micro-particle aggregate is capable of adsorbing a pluralityof organophilic active ingredients.

SUMMARY OF THE INVENTION

It was unexpectedly discovered that the process of the present inventionis capable of producing micro-particles and micro-particle aggregatesthat have a high compound adsorbency for oleophilic compounds, and canbe manufactured in a variety of particle size distributions by aprecipitation polymerization process.

The present invention is directed to a process for making a porouspolymer aggregate formed from a plurality of micro-particles thatexhibits a high oil adsorbency. The method of the present inventioncomprises the steps of:

dissolving at least one and preferably at least two polyunsaturatedmonomers, preferably also an effective amount of an organicpolymerization initiator, in a water-immiscible organic solvent and asilicone solvent that is inert (not reactive) with respect to themonomers and resulting polymer to provide a monomer mixture; in thepreferred embodiment, the silicone solvent also acts as a solvent sothat a separate solvent is not needed;

continuing agitation at a rate that does not break the aggregates intosmaller aggregates or individual spheres, for example, using a tip speedfor a rotating paddle impeller of about 0.1 to 0.2 meters per second upto about 15 meters per second, e.g., 30 rpm, during polymerization ofthe monomers in the suspended micro-droplets to produce microporouspolymer micro-particles, and micro-particle aggregates in the form ofaggregated spheres having an interior void volume surrounded by theaggregated spheres; and

separating the microporous polymer micro-particle aggregates from theorganic solvent to produce microporous, oil adsorbent polymermicro-particles having a diameter of about 0.1 to about 100 microns,preferably about 0.1 to about 80 microns. The aggregates, or assembliesof micro-particles, can be manufactured to have diameters of about 1 toabout 500 μm and new and unexpected adsorptive capacity for oleophiliccompounds, in both solid and liquid forms. Preferably more than 99% ofthe aggregates and agglomerates are smaller than 500 μm, preferably lessthan about 100 μm.

The present invention is further directed to microporous, oil adsorbentmicro-particles and micro-particle aggregates of a polymer comprising atleast one and preferably at least two polyunsaturated monomers, themicro-particles and micro-particle aggregates characterized by having avoid volume surrounded by aggregated micro-particle spheres and having amean unit micro-particle diameter of less than about 10 microns,preferably less than about 8 microns, having a total adsorption capacityfor organic liquids, e.g., mineral oil that is at least 80% by weight,preferably at least about 85% by weight, based on the total weight ofadsorptive micro-particles plus adsorbed oil. In a preferred embodiment,the micro-particle assemblies, or aggregated spheres of micro-particlesof the present invention are characterized by a mean unit diameter fromabout 5 to about 500 microns, preferably about 5μm to about 100 μm, someaggregates having a diameter of about 2 to about 100 μm, others havingdiameters from about 20 to about 80 microns.

BRIEF DESCRIPTION OF TIE DRAWINGS

FIGS. 1 and 2 are graphs showing the time release of Silicone Fluid (DC244) and vitamin g acetate, respectively, from the Poly-Pore L ofExample 1, (tested under 10 liter/min air velocity), compared tovaporization of these materials from a non-sorbent open dish (blank);and

FIGS. 3-5 are photographs of the micro-particles of Example 1 magnified100, 1500 and 10000 times, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present invention has two aspects. In its first aspect, it isdirected to a process for making a polymer by the precipitationpolymerization process in a porous micro-particle form, includingaggregates of the micro-particles, and assemblies or clusters ofaggregates that are capable of sorbing high volumes of oleophilic(hydrophobic) compounds in solid and/or liquid forms. Oleophiliccompounds are adsorbed in an open interior area surrounded by aggregatedmicro-particles. The preferred process of the present inventioncomprises the steps of:

dissolving at least one and preferably at least two polyunsaturatedmonomers, preferably along with an effective amount of an organicpolymerization initiator, in a water-immiscible silicone fluid solvent,to provide a monomer mixture;

slowly agitating the dissolved monomers and silicone solvent;

continuing slow agitation during polymerization of the monomers in thesilicone fluid to produce microporous polymer micro-particles andagglomerates thereof; and

separating the microporous polymer micro-particles and agglomerates fromthe silicone solvent to produce microporous, oil adsorbent polymermicro-particles and aggregates in the form of spheres, sphere aggregatesand sphere agglomerates having a diameter of less than about 500microns, preferably less than about 100 microns, more preferably lessthan about 80 microns, and a new and unexpected adsorptive capacity foroleophilic compounds, in both solid and liquid forms.

The term "sorptive" (or "sorption") is used herein to refer to thecapability or capacity of the micro-particles of the present inventionto both adsorb and absorb oleophilic materials. However, the amount oforganic (oleophilic) liquid that is absorbed is negligible in comparisonto the amount of solids and/or liquids that are adsorbed betweenagglomerated spherical micro-particles. In discussing micro-particles,the art loosely uses the term "adsorptive," such as in "total adsorptivecapacity" or in "free flowing adsorptive capacity." However, it isunderstood that references in the art to "total adsorptive capacity"inherently include the total absorptive and adsorptive capacities of aparticle, unless otherwise defined. Likewise, references in the art to"free flowing adsorptive capacity" also inherently include both theabsorptive and adsorptive capacities.

The process of the present invention copolymerizes at least one andpreferably at least two polyunsaturated (polyethylenically unsaturated)monomers, preferably allyl methacrylate, and an ethylene glycoldimethacrylate. Both the allyl methacrylate and the ethylene glycoldimethacrylate are diunsaturated monomers. The diunsaturated monomersalso function as cross-linking agents.

The highly cross-linked polymeric micro-particles of this invention areprepared by polymerizing one and preferably at least two monomers havingat least two unsaturated bonds (hereinafter referred to as"polyunsaturated" monomers) said monomers being polymerized including nomore than about 40%, preferably no more than about 9% by total monomerweight of monounsaturated comonomers. Examples of polyunsaturatedmonomers can be poly-acrylates ("poly" meaning two or more),-methacrylates, or -itaconates of: ethylene glycol, propylene glycol;di-, tri-, tetra-, or poly-ethylene glycol and propylene glycol;trimethylol propane, glycerine, erythritol, xylitol, pentaerythritol,dipentaerythritol, sorbitol, mannitol, glucose, sucrose, cellulose,hydroxyl cellulose, methyl cellulose, 1,2 or 1,3 propanediol, 1,3 or 1,4butanediol, 1,6 hexanediol, 1,8 octanediol, cyclohexanediol, orcyclohexanetriol. Similarly, bis(acrylamido or methacrylamido) compoundscan be used. These compounds are, for example, methylene bis(acryl ormethacryl)amide, 1,2 dihydroxy ethylene bis(acryl or methacryl)amide,hexamethylene bis(acryl or methacryl)amide.

Another group of useful monomers could be represented by di or polyvinyl esters, such as divinyl propylene urea, divinyl-oxalate,-malonate, -succinate, -glutamate, -adipate, -sebacate, -maleate,-fumerate, -citraconate, and -mesaconate.

Other suitable polyunsaturated monomers include divinyl benzene, divinyltoluene, diallyl tartrate, allyl pyruvate, allyl maleate, divinyltartrate, triallyl melamine, N,N'-methylene bis acrylamide, glycerinedimethacrylate, glycerine trimethacrylate, diallyl maleate, divinylether, diallyl monoethyleneglycol citrate, ethyleneglycol vinyl allylcitrate, allyl vinyl maleate, diallyl itaconate, ethyleneglycol diesterof itaconic acid, divinyl sulfone, hexahydro 1,3,5-triacryltriazine,triallyl phosphite, diallyl ether of benzene phosphonic acid, maleicanhydride triethylene glycol polyester, polyallyl sucrose, polyallylglucose, sucrose diacrylate, glucose dimethacrylate, pentaerythritoldi-, tri- and tetra- acrylate or methacrylate, trimethylol propane di-and triacrylate or methacrylate, sorbitol dimethacrylate,2-(1-aziridinyl)-ethyl methacrylate, tri-ethanolamine diacrylate ordimethacrylate, triethanolamine triacrylate or trimethacrylate, tartaricacid dimethacrylate, triethyleneglycol dimethacrylate, thedimethacrylate of bis-hydroxy ethylacetamide and the like.

Other suitable polyethylenically unsaturated cross-linking monomersinclude ethylene glycol diacrylate, diallyl phthalate,trimethylolpropanetrimethacrylate, polyvinyl and polyallyl ethers ofethylene glycol, of glycerol, of pentaerythritol, of diethyleneglycol,of monothio- and dithio-derivatives of glycols, and of resorcinol;divinylketone, divinylsulfide, allyl acrylate, diallyl fumarate, diallylsuccinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyladipate, diallyl sebacate, diallyl tartrate, diallyl silicate, triallyltricarballylate, triallyl aconitrate, triallyl citrate, triallylphosphate, divinyl naphthalene, divinylbenzene, trivinylbenzene;alkyldivinylbenzenes having from 1 to 4 alkyl groups of 1 to 2 carbonatoms substituted on the benzene nucleus; alkyltrivinylbenzenes having 1to 3 alkyl groups of 1 to 2 carbon atoms substituted on the benzenenucleus; trivinylnaphthalenes, and polyvinylanthracenes. In addition,acryl or methracryl end-capped siloxanes and polysiloxanes, methacryloylend-capped urethanes, urethane acrylates of polysiloxane alchols andbisphenol A bis methacrylate and ethoxylated bisphenol A bismethacrylate also are suitable as polyunsaturated monomers.

Still another group of monomers is represented by di or poly vinylethers of ethylene, propylene, butylene, and the like, glycols,glycerine, penta erythritol, sorbitol, di or poly allyl compounds suchas those based on glycols, glycerine, and the like, or combinations ofvinyl allyl or vinyl acryloyl compounds such as vinyl methacrylate,vinyl acrylate, allyl methacrylate, allyl acrylate, methallylmethacrylate, or methallyl acrylate. In addition, aromatic,cycloaliphatic and heterocyclic compounds are suitable for thisinvention. These compounds include divinyl benzene, divinyl toluene,divinyl diphenyl, divinyl cyclohexane, trivinyl benzene, divinylpyridine, and divinyl piperidine. Furthermore, divinyl ethylene ordivinyl propylene urea and similar compounds may be used, e.g., asdescribed in U.S. Pat. Nos. 3,759,880; 3,992,562; and 4,013,825, whichare hereby incorporated by reference. Acryloyl- or methacryloylend-capped siloxane and polysiloxanes such as those described in U.S.Pat. Nos. 4,276,402; 4,341,889, French Patent 2,465,236, and GermanPublication GER OLS Patent 3,034,505, which are hereby incorporated byreference, are suitable for this invention. Methacryloyl end-cappedurethanes, such as those described in U.S. Pat. Nos. 4,224,427;4,250,322; and 4,423,099, German Publications GER OLS No. 2,365,631 and2,542,314, Japanese Patent Application Nos. 85/233,110; 86/09,424, and86/30,566, and British Patent 1,443,715, are suitable for thisinvention. Urethane acrylates of polysiloxane alcohols as described inU.S. Pat. Nos. 4,543,398 and 4,136,250 and bisphenol A bis methacrylateand ethoxylated bisphenol A bis methacrylate are also suitable monomersfor this invention.

Monoethylenically unsaturated monomers suitable, in an amount up toabout 40% by weight, preferably no more than about 9% by weight, basedon the total weight of monomers, for preparing polymer micro-particlesinclude ethylene, propylene, isobutylene, disobutylene, styrene, vinylpyridine ethylvinylbenzene, vinyltoluene, and dicyclopentadiene; estersof acrylic and methacrylic acid, including the methyl, ethyl, propyl,isopropyl, butyl, sec-butyl, tert-butyl, amyl, hexyl, octyl, ethylhexyl,decyl, dodecyl, cyclohexyl, isobornyl, phenyl, benzyl, alkylphenyl,ethoxymethyl, ethoxyethyl, ethoxyproyl, propoxymethyl, propoxyethyl,propoxypropyl, ethoxyphenyl, ethoxybenzyl, and ethoxycyclohexyl esters;vinyl esters, including vinyl acetate, vinyl propionate, vinyl butyrateand vinyl laurate, vinyl ketones, including vinyl methyl ketone, vinylethyl ketone, vinyl isopropyl ketone, and methyl isopropenyl ketone,vinyl ethers, including vinyl methyl ether, vinyl ethyl ether, vinylpropyl ether, and vinyl isobutyl ether; and the like.

Other monounsaturated monomer materials which may be utilized inaccordance with the present invention, in an amount up to about 40% byweight or less, preferably no more than about 25% by weight, and mostpreferably no more than about 9% by weight, based on the total weight ofmonomers in the monomer solution, include hydroxy alkyl esters of alpha,beta-unsaturated carboxylic acids such as 2-hydroxy ethylacrylate ormethacrylate, hydroxypropylacrylate or methacrylate and the like. Manyderivatives of acrylic or methacrylic acid other than the estersmentioned are also suitable as starting monounsaturated monomermaterials for use in forming the unsaturated polymer micro-particles ofthe present invention. These include, but are not limited to thefollowing monomers: methacrylylglycolic acid, the monomethacrylates ofglycol, glycerol, and of other polyhydric alcohols, themonomethacrylates of dialkylene glycols and polyalkylene glycols, andthe like. The corresponding acrylates in each instance may besubstituted for the methacrylates. Examples include the following:2-hydroxyethyl acrylate or methacrylate, diethylene glycol acrylate ormethacrylate, 2-hydroxypropyl acrylate or methacrylate, 3-hydroxypropylacrylate or methacrylate, tetraethyleneglycol acrylate or methacrylate,pentaethyleneglycol acrylate or methacrylate, dipropyleneglycol acrylateor methacrylate, acrylamide, methacrylamide, diacetone acrylamidemethylolacrylamide methylolmethacrylanide and any acrylate ormethacrylate having one or more straight or branched chain alkyl groupsof 1 to 30 carbon atoms, preferably 5 to 18 carbon atoms, and the like.Other suitable examples include isobornyl methacrylate, phenoxyethylmethacrylate, isodecyl methacrylate, stearyl methacrylate, hydroxypropylmethacrylate, cyclonexyl methacrylate, dimethylaminoethyl methacrylate,t-butylaminoethyl methacrylate, 2-acrylamido propane sulfonic acid,2-ethylexyl methacrylate, methyl methacrylate, ethyl methacrylate, butylmethacrylate, 2-hydroxyethyl methacrylate, tetrahydrofurfurylmethacrylate and methoxyethyl methacrylate.

Examples of monounsaturated monomers containing carboxylic acid groupsas functional groups and suitable for use as starting materials inaccordance with the invention include the following: acrylic acid,methacrylic acid, itaconic acid, aconitic acid, cinnamic acid, crotonicacid, mesaconic acid, maleic acid, fumaric acid and the like.

Partial esters of the above acids are also suitable as monosaturatedmonomers for use in accordance with the invention. Instances of suchesters include the following: mono-2-hydroxypropyl aconitate,mono-2-hydroxyethyl maleate, mono-2-hydroxypropyl fumarate, mono-ethylitaconate, monomethyl cellosolve ester of itaconic acid, monomethylcellosolve ester of maleic acid, and the like.

Instances of suitable monounsaturated monomers containing amino groupsas functional groups include the following: diethylaminoethyl acrylateor methacrylate, dimethylaminoethyl acrylate or methacrylate,monoethylaminoethyl acrylate or methacrylate, tert. butylaminoethylmethacrylate, para-amino styrene, ortho-amino styrene, 2-amino-4-vinyltoluene, piperidinoethyl methacrylate, morpholinoethyl methacrylate,2-vinyl pyridine, 3-vinyl pyridine, 4-vinyl pyridine, 2-ethyl-5-vinylpyridine, dimethylaminopropyl acrylate and methacrylate,dimethylaminoethyl vinyl ether, dimethylaminoethyl vinyl sulfide,diethylaminoethyl vinyl ether, amonoethyl vinyl ether,2-pyrrolidinoethyl methacrylate,3-dimethylaminoethyl-2-hydroxy-propylacrylateormethacrylate,2-aminoethyl acrylate or methacrylate, isopropyl methacrylamide,N-methyl acrylamide or methacrylamide, 2-hydroxyethyl acrylamide ormethacrylamide, 1-methacryloyl-2-hydroxy-3-trimethyl ammonium chlorideor sulfomethylate, 2-(1-aziridinyl)-ethyl methacrylate, and the like.Polyethylenically unsaturated monomers which ordinarily act as thoughthey have only one unsaturated group, such as isopropene, butadiene andchloroprene, should not be calculated as part of the polyunsaturatedmonomer content, but as part of the monoethylenically unsaturatedmonomer content.

The process of the present invention preferably utilizes an effectiveamount of an organic polymerization initiator to cause polymerization tooccur in the organic phase solvent. However, other methods of initiatingpolymerization may be used instead, such as UV light, actinic radiation,or the like. By way of example, suitable organic initiators include theorganic peroxide initiators, such as dibenzoyl peroxide or t-butylperoctoate, or the azo initiators. Preferred initiators are the azoinitiators such as 2,2'-azobisisobutyronitrile and2,2'-azobis(2,4-dimethylpentanenitrile). An especially preferred azoinitiator is 2,2'-azobis(2,4-dimetylpentanenitrile), which iscommercially available under the tradename VAZO 52 from DuPont,Wilmington, Del. A typical effective amount of organic initiatorrelative to dry monomer was found to be about 0.5-2% by weight,preferably about 1-1.2% by weight.

Examples of redox systems include secondary or tertiary amines and amine(preferably tertiary) and peroxide combinations. The ratio between theperoxide and the amine may vary, for example, from 0.1 to 5 moles ofamine per mole of peroxide. It is useful to first dissolve the peroxidein a part of the solvent, and separately dissolve the amine in the otherpart of the solvent, then mix the peroxide part with the monomersolution at room temperature and, subsequently, add the amine part. Thecharging of the peroxide and amine part can be done at the beginning ofthe reaction or in portions throughout the reaction period. These aminesare generally of the formula R₂ NH or R₃ N wherein R is an alkyl orsubstituted alkyl, cycloalkyl, or aryl group. Preferably the amine is atertiary amine.

Illustrative reducing agents of this invention are methylbutyl amine,bis(2-hydroxyethyl)butyl amine, butyldimethyl amine, dimethyl amine,dibenzylethyl amine, diethylmethyl amine, dimethylpentyl amine, diethylamine, 2,2', 2"-trihydroxy dipropyl ethyl amine, di-n-propylene amine,2,2',2"-trimethyl tributyl amine, triethyl amine, dimethyl aminoacetal,pentylhexyl amine, triethanolamine, trihexyl amine, trimethyl amine,trioctadecyl amine, tripropyl amine, trisopropyl amine, tetramethylenediamine, and esters of para-amino benzoic acid, e.g., p-dimethylamino-2-ethylhexyl-benzoate, dimethyl aminoethyl acetate,2-(n-butoxy)ethyl 4-dimethylaminobenzoate, 2-(dimethylamino)ethylbenzoate, ethyl-4-dimethylaminobenzoate, methyldiethanolamine, dibutylamine, N,N-dimethylbenzylamine, methylethyl amine, dipentyl amine andperoxide Fe²⁺.

Other preferred initiators are selected from inorganic initiators suchas sodium, potassium, or ammonium persulfates and hydrogen peroxide.

In the preferred process of the present invention, the monomers and theorganic initiator are dissolved in a silicone solvent to produce theorganic phase. Suitable silicone solvents are disclosed in U.S. Pat. No.5,189,012, hereby incorporated by reference. Other substantiallywater-immiscible organic solvents, including the aliphatic and aromatichydrocarbons, can be combined with the silicone solvent. Typical ofthese solvents are toluene, cyclohexane, fluoro silicones, chlorinatedsolvents, such as trichlorethylene, trichlormethane, dichlormethane, andthe like, and one or more of the heptanes, alone or in combination.

Polymerization is accomplished by dissolving the monomers or theirmixtures in an inert silicone solvent which does not react with themonomers or the resulting polymer. Based on the parts by weight of themonomer and the solvent totalling 100 parts by weight, the monomers areused from 0.1 to less than 25 parts by weight, preferably, from 2 toless than 25 parts by weight, and, more preferably, from 5 to 20 partsby weight. Correspondingly, the solvent is present from greater than 60parts by weight, preferably greater than 70 parts by weight, morepreferably greater than 75-80 parts by weight to 99.9 parts by weight,preferably, from greater than about 75 parts by weight to about 98 partsby weight, and, most preferably, from about 80 parts by weight to about95 parts by weight. No surfactant or dispersing aid is required.Preferred silicone solvents include those solvents disclosed in U.S.Pat. No. 5,189,102, hereby incorporated by reference.

Preferably, the solvent is relatively volatile, having a boiling pointof less than about 200° C., preferably less than about 180° C. at oneatmosphere and is water-miscible. The removal of the solvent can beaccomplished by evaporation, e.g., by heat and/or vacuum, or the solventcan be left adsorbed between agglomerated polymeric micro-particles. Thepolymer can be washed with a suitable solvent, e.g., the same solventused in polymerization, before it is dried.

Suitable solvents that can be used in addition to the silicone solventinclude a wide range of substances, notably inert, non-polar organicsolvents. Some of the most convenient examples are alkanes,cycloalkanes, and aromatics. Specific examples of such solvents arealkanes of from 5 to 12 carbon atoms, straight or branched chaincycloalkanes of from 5 to 8 carbon atoms, benzene, and alkyl-substitutedbenzenes, such as toluene and the xylenes.

Solvents of other types include C₄ -C₂₀ alcohols, perfluoro polyethers,and silicone oils. Examples of silicone oils arepolydimethylcyclosiloxane, hexamethyldisiloxane, cyclomethicone,dimethicone, amodimethicone, trimethylsilylamodimethicone,polysiloxane-polyalkyl copolymers (such as stearyl dimethicone and cetyldimethicone), dialkoxydimethylpolysiloxanes (such as stearoxydimethicone), polyquarternium 21, dimethicone propyl PG-betaine,dimethicone copolyol and cetyl dimethicone copolyol. Removal of thesolvent may be effected by solvent extraction, evaporation, or similarconventional operations.

In performing the process of the present invention, the dissolvedmonomer(s) in the silicone solvent phase is polymerized under an inert(e.g., Argon or Nitrogen) atmosphere.

The polymerization reaction is allowed to proceed in the slowly agitated(e.g., 10-100 rpm stirring paddle) reaction mixture by raising thereaction temperature. As disclosed in Example 1, at about 46° C., somepolymerization was observed in the stirred reaction mixture. At about53° C., massive polymerization was observed. The mixture is thenpreferably heated to 60° C.-75° C. to drive the polymerization reactionto completion.

Once polymerization is completed, the resulting microporous polymermicro-particles and micro-particle aggregates are separated from thereaction mixture, such as by filtering or by screening. Once the polymermicro-particles and aggregates thereof have been separated from thewater-immiscible organic solvent, they become the oil adsorbent polymermicro-particles of the present invention--the exterior of the spheresadsorbing oleophilic compounds within an interior space defined betweenaggregated and agglomerated unit micro-particles, surrounded byaggregated micro-particles, capable of entrapping solids and liquidscontaining oleophilic compounds far better than prior artmicro-particles.

Thus, the present invention is also directed to a composition ofmatter--microporous and oil adsorbent micro-particles and aggregatesthereof in the form of micro-particle spheres, and aggregates thereof,comprising a polymer formed by polymerizing at least two polyunsaturatedmonomers (each containing at least two carbon to carbon double bonds)optionally including one or more monounsaturated monomers, in an amountup to about 40% by weight, preferably no more than about 9% by weight,based on the total weight of monomers. The resulting micro-particles, inthe form of spheres having a mean unit diameter of less than about 2microns, preferably less than about 1 micron, have a total adsorptioncapacity for mineral oil that is at least about 80% by weight,preferably at least about 85% by weight, based upon the total weight ofthe polymer plus adsorbed oil. The phrase mean "unit diameter" refers tomean diameter of the individual particle and not to the diameter ofagglomerates. The mean unit diameter of the individual micro-particlesis more preferably from about 0.5 to about 2 microns; most preferably,from about 0.5 to about 1 micron; while the mean diameter of theaggregates preferably is about 5 to about 20 microns, preferably about 5to about 12 microns.

Preferably, the micro-particles of the present invention have a totalsorption capacity for mineral oil of about 82-93% by weight; morepreferably, about 84% by weight or greater; most preferably about 85-93%by weight or greater.

The micro-particles of the present invention appear as a white powderand constitute free flowing discrete solid particles even when loadedwith a lipophilic material to their "free flowing" sorption capacity. Inpreferred microporous and oil sorbent micro-particles of the presentinvention, two diunsaturated monomers--one of the polyunsaturatedmonomers being an ethylene glycol dimethacrylate, preferablymonoethylene glycol dimethacrylate is polymerized with anotherpolyunsaturated monomer, e.g., allyl methacrylate. The preparation ofsuch a micro-particle is described in Example 4 herein, wherein theother diunsaturated monomer is allyl methacrylate in a preferred moleratio of about 1:1.2 allyl methacrylate: monoethylene glycoldimethacrylate.

Table I compares the oil adsorption of the micro-particles of theExamples to the reported oil adsorption for the copolymermicro-particles of U.S. Pat. No. 4,962,133, and to that of acommercially available oil sorbent product. Table I establishes that thepolymers of the present invention, containing polyunsaturatedmonomer(s), have a superior total adsorption capacity for mineral oilover the copolymers of the prior art, e.g., DC 6603. In particular, thepolymer of Example 1 exhibited a total sorption capacity for mineral oilof 91.1% by weight, compared to 89.6% by weight for LMA/EGDM copolymerand 83.5% by weight for the commercially available product (Dow CorningProduct No. 6603).

    ______________________________________                                        BMA          butyl methacrylate                                               EGDMA        monoethylene glycol dimethacrylate                               AMA          allyl methacrylate                                               MMA          methyl methacrylate                                              ______________________________________                                    

EXAMPLE 1

An oleophilic porous terpolymer was produced by the precipitationpolymerization technique by slow mixing in 2000 milliliterpolymerization reactor equipped with a paddle type stirrer, 1.80 gramsof butyl methacrylate monomer or 5.9 mole percent, 10.75 grams of allylmethacrylate monomer, or 39.4 mole percent, and 23.45 grams of ethyleneglycol dimethacrylate monomer, or 54.7 mole percent. Cyclomethicon DC244 fluid as the solvent was added to the reactor in the amount of 564grams. The monomers were soluble in the solvent. The mixture includingmonomers, solvent, and 0.72 grams of catalytic initiator VAZO 52, waspurged with Argon. At the stirring speed of 30 rpm the system was heatedabout 45° C. until polymerization was initiated, at which time thetemperature was increased to 65° C. for six hours, in order to completethe polymerization. During this time, the terpolymer precipitated fromthe solution. The polymerization produced unit particles of a diameterless than about one micron. Some of the unit particles adhered togetherproviding agglomerates of the order of magnitude of about 20 to 80microns in diameter. Some of the agglomerates adhered further and werefused and welded one to another forming aggregates of loosely heldassemblies of agglomerates of the order of magnitude of about 200 to 800microns in diameter. The mixture was filtered to remove excess solvent,and a wet powder cake was tray dried in a vacuum oven. A dry hydrophobicterpolymeric powder consisting of unit-particles, agglomerates, andaggregates was isolated.

The total adsorption capacity was determined by addition of incrementalamount of liquid (mineral oil) to a known amount of powder, using gentlemixing until the powder was no longer free flowing and yet absorbingliquid. The total adsorption capacity was determined by the followingcalculation: ##EQU1##

EXAMPLE 2

Example 1 was repeated for each of a series of monomer systems shown inTable 1. In each instance, submicron sized copolymeric powders wereproduced employing a stirring speed of about 30 rpm. The initiator wasVAZO 52. Adsorption capacities of the various polymeric powders formineral oil were determined and are shown in the Table, along with themole ratios of monomers.

EXAMPLE 3

The equipment of Example 1 was employed and 12.585 grams of allylmethacrylate monomer, or 46 mole percent, and 23.45 grams of ethyleneglycol dimethacrylate monomer, or 54 mole percent, were copolymerized.

The result of adsorption capacity for mineral oil using various monomersis shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                             Total                                                                         Adsorption                                                                    Capacity                                                                      For                                                                           Mineral                                                             Mole      Oil       Bulk  Adsorption                                          Percent   % By      Density                                                                             Capacity                                 Monomer    Ratio     Weight    g/cm.sup.3                                                                          g/g                                      ______________________________________                                        BMA/AMA/EGDM                                                                              6/39/55  90.4      0.0332                                                                              9.4                                      BMA/AMA/EGDM                                                                              5/40/55  90.3      0.0317                                                                              9.3                                      BMA/AMA/EGDM                                                                             30/14/56  90.4      0.0351                                                                              9.4                                      AMA/EGDM   46/54     91.1      0.0360                                                                              10.3                                     LMA/AMA/EGDM                                                                              1/44/56  90.1      0.0331                                                                              9.1                                      LMA/AMA/EGDM                                                                             1.5/43.5/55                                                                             90.7      0.0366                                                                              9.7                                      LMA/AMA/EGDM                                                                              2/43/55  91.7      0.0363                                                                              11.00                                    LMA/AMA/EGDM                                                                              3/41/56  91.5      0.0373                                                                              10.8                                     LMA/AMA/EGDM                                                                              4/39/56  90.9      0.0369                                                                              10.0                                     LMA/EGDM   20/80     89.6      0.0391                                                                              8.6                                      DC 6603    --        83.5      0.0712                                                                              5.1                                      (competitor)                                                                  ______________________________________                                         The abbreviations used in Table 1 are:                                        BMA  butyl methacrylate                                                       LMA  lauryl methacrylate                                                      AMA  allyl methacrylate                                                       EGDM  ethylene glycol dimethacrylate                                     

EXAMPLE 4

(Poly-Pore™ L 200)

An oleophilic porous copolymer was produced by the precipitationpolymerization technique by slow mixing in 2 liter polymerizationreactor equipped with a paddle type stirrer, 12.55 grams of allylmethacrylate or 46 mole percent, and 23.45 grams of ethylene glycoldimethacrylate or 54 mole percent. Cyclomethicon DC 244 fluid as thesolvent was added to the reactor in the amount of 564 grams. Themonomers were soluble in the solvent. The mixture including monomers,solvent and 0.72 grams of catalytic initiator VAZO 52, was purged withArgon. At the stirring speed of 30 rpm the system was heated about 45°C. until polymerization was initiated, at which time, the temperaturewas increased to 65° C. for six hours in order to complete thepolymerization. During this time, the polymer precipitated from thesolution. The polymerization produced unit particles of a diameter lessthan about one micron. Some of the unit particles adhered further andwere fused and welded one to another forming aggregates of loosely heldassemblies of agglomerates of the order of the magnitude of about 5 toabout 100, preferably about 5 to about 80 microns, microns in diameter.The mixture was filtered to remove excess solvent, and a wet powder cakewas try dried in a vacuum oven. A dry hydrophobic polymeric powderconsisting of unit particles, agglomerates, and aggregates, or clustersof agglomerates, was isolated, having a total adsorption capacity forlight mineral oil of 11.2 grams per gram of polymer, and apparentdensity of 0.034 g/cm³. The particles had a particle size distributionas follows:

    __________________________________________________________________________    High                                                                             Under                                                                             High                                                                             Under                                                                             High                                                                             Under                                                                             High                                                                             Under                                                                             High                                                                             Under                                                                             High                                                                             Under                                   Size                                                                             %   Size                                                                             %   Size                                                                             %   Size                                                                             %   Size                                                                             %   Size                                                                             %                                       __________________________________________________________________________    80.0                                                                             100 24.9                                                                             93.3                                                                              7.75                                                                             51.3                                                                              2.41                                                                             9.2 0.75                                                                             3.6 0.23                                                                             0.7                                     71.9                                                                             99.8                                                                              22.4                                                                             91.7                                                                              6.97                                                                             45.7                                                                              2.17                                                                             7.9 0.68                                                                             3.3 0.21                                                                             0.5                                     64.7                                                                             99.7                                                                              20.1                                                                             89.6                                                                              6.27                                                                             40.3                                                                              1.95                                                                             6.9 0.61                                                                             3.0 0.19                                                                             0.4                                     58.2                                                                             99.4                                                                              18.1                                                                             87.2                                                                              5.64                                                                             35.1                                                                              1.75                                                                             6.2 0.55                                                                             2.7 0.17                                                                             0.3                                     52.3                                                                             99.0                                                                              16.3                                                                             84.2                                                                              5.07                                                                             30.2                                                                              1.58                                                                             5.6 0.49                                                                             2.4 0.15                                                                             0.2                                     47.1                                                                             98.6                                                                              14.6                                                                             80.7                                                                              4.56                                                                             25.6                                                                              1.42                                                                             5.2 0.44                                                                             2.1 0.14                                                                             0.1                                     42.3                                                                             98.0                                                                              13.2                                                                             76.7                                                                              4.10                                                                             21.6                                                                              1.28                                                                             4.8 0.40                                                                             1.8 0.12                                                                             0.1                                     38.1                                                                             97.4                                                                              11.8                                                                             72.2                                                                              3.69                                                                             18.2                                                                              1.15                                                                             4.5 0.36                                                                             1.5 0.11                                                                             0.0                                     34.2                                                                             96.6                                                                              10.7                                                                             67.4                                                                              3.32                                                                             15.3                                                                              1.03                                                                             4.3 0.32                                                                             1.3 0.10                                                                             0.0                                     30.8                                                                             95.7                                                                              9.58                                                                             62.2                                                                              2.98                                                                             12.8                                                                              0.93                                                                             4.1 0.29                                                                             1.1                                            27.7                                                                             94.6                                                                              8.62                                                                             56.9                                                                              2.68                                                                             10.8                                                                              0.83                                                                             3.8 0.26                                                                             0.9                                            __________________________________________________________________________

The total adsorption capacity was determined by addition of incrementalamounts of liquid (mineral oil) to a known amount of powder, usinggentle mixing, until the powder was no longer free flowing and yetadsorbing liquid. The adsorption capacities for various olephilicmaterials are as follows:

    ______________________________________                                                       Total (g/g)                                                                          Free-Flowing (g/g)                                      ______________________________________                                        Water             0.0     0.0                                                 Mineral Oil      11.6     9.0                                                 Artificial Sebum 12.6     9.5                                                 Glycerin         10.0     7.6                                                 Cyclomethicone (DC244)                                                                         15.0     10.8                                                Isopropyl Myristate                                                                            11.4     9.5                                                 Vitamin E Acetate                                                                               9.2     7.0                                                 Benzophenone-3   12.8     9.1                                                 PEG 200          13.2     9.8                                                 Benzyl Acetate   12.7     9.9                                                 Fragrance/Floral Lavender                                                                      12.7     9.6                                                 (Q-12512)                                                                     Dimethicone (DCC 10)                                                                           14.1     10.5                                                Dimethicone (DCC 200)                                                                          14.0     9.1                                                 Dimethicone (DCC 350)                                                                          12.5     8.9                                                 Dimethicone (DCC 1000)                                                                         12.1     8.6                                                 Motor oil (low 40)                                                                             10.8                                                         Heptane           9.3                                                         Toluene          10.8                                                         Xylene           10.7                                                         Methylene Chloride                                                                             20.0                                                         Irgasan DP300    10.7                                                         5-chloro-2-(2,4 dichloro-                                                     phenoxy) phenol                                                               ______________________________________                                    

EXAMPLE 5

The copolymer of Example 4 was loaded with methanol/salicylic acidsolution to a content of 12 grams per gram, and dried in an oven at 80°C. to evaporate methanol. The dry polymeric powder was white, finepowder, with 78.3% entrapped salicylic acid, i.e., 2.8 grams per gram.Entrapped salicylic acid is not light sensitive, nor explosive, whereasfree salicylic acid is both light sensitive and explosive. Salicylicacid is an antiseptic and antifungal agent.

EXAMPLE 6

A solution was made by dissolving 1 gram of dibenzoyl peroxide in 8grams of chloroform. The solution was adsorbed in 1 gram of polymer ofExample 4, thereafter chloroform was evacuated, and entrapped dibenzoylperoxide polymer system was pulverized to very fine white powder.Usually dibenzoyl peroxide is shock sensitive and has a tendency toexplode at contact with metals. The entrapped dibenzoyl peroxide polymersystem was inactive to friction, to shock and to contact with metals,whereas, free dibenzoyl peroxide is explosive. The loading capacity ofdibenzoyl peroxide was 50%, i.e., 1 gram per gram.

EXAMPLE 7

Retinol was dissolved in same amount of ether 5.5 grams of the solutionwas adsorbed in 1 gram of the polymer powder of Example 4. Thereafterether was evacuated by vacuum and free flowing light yellow powder wasobtained. The Retinol capacity was 2.75 grams per gram, i.e., 73%.Usually Retinol is in form of sticky crystals, it is light sensitive,and skin irritant, is used in cosmetic formulations and as vitamin.

What is claimed is:
 1. A microporous and oil sorbent micro-particlecomprising a polymer of allyl methacrylate and an ethylene glycoldimethacrylate, in a mole ratio of about 1:1 to about 1:2, said particlecharacterized by having a mean unit diameter of less than about 80microns, a bulk density of about 0.02 to about 0.1 g/cm³, and a totaladsorption capacity for mineral oil that is 80% by weight or greater,based on the total weight of polymer and adsorbed oil.
 2. Themicro-particle of claim 1, wherein the total adsorption capacity formineral exceeds 85%.
 3. The micro-particle of claim 2, wherein the totaladsorption capacity for mineral exceeds 90%.
 4. The micro-particle ofclaim 1, wherein said ethylene glycol dimethacrylate is a memberselected from the group consisting of monoethylene glycoldimethacrylate, diethylene glycol dimethacrylate and triethylene glycoldimethacrylate.
 5. The micro-particle of claim 4, wherein said ethyleneglycol dimethacrylate is monoethylene glycol dimethacrylate.
 6. Themicro-particle of claim 3, wherein said total adsorption capacity formineral oil is 85-93% by weight or greater, based on the weight ofpolymer plus adsorbed mineral oil.
 7. The micro-particle of claim 1,wherein the mean unit particle diameter is from about 1 to about 20microns.
 8. The micro-particle of claim 1 wherein the bulk density isabout 0.02 gm/cm³ to about 0.07 gm/cm³.
 9. The micro-particle of claim 1wherein said bulk density is about 0.02 to about 0.05 g/cm³.
 10. Themicro-particle of claim 1 wherein the ratio of allyl methacrylate toethylene glycol dimethacrylate is about 1:1.2.
 11. The micro-particle ofclaim 1 wherein the polymer is free of a monounsaturated monomer. 12.The micro-particle of claim 1 wherein the polymer contains a C₁ to C₄ester of acrylic acid, a C₁ to C₄ ester of methacrylic acid, or amixture thereof, in an amount up to about 9% by weight, based on thetotal weight of the monomers.
 13. The micro-particle of claim 1 whereinthe mean unit particle diameter is from about 1 to about 50 microns. 14.The micro-particle of claim 1 wherein the particle diameter is fromabout 0.1 to about 100 microns.
 15. The micro-particle of claim 11wherein the particle diameter is from about 0.1 to less than about 2microns.
 16. A microporous and oil sorbent micro-particle comprising apolymer of allyl methacrylate and a second diunsaturated monomer in amole ratio of the allyl methacrylate to the second monomer of about 1:1to about 1:2, said particle having a mean unit diameter of less thanabout 80 microns, a bulk density of about 0.02 to about 0.1 g/cm³, and atotal adsorption capacity for mineral oil that is 80% by weight orgreater, based on the total weight of polymer and adsorbed oil.
 17. Themicroparticle of claim 16 wherein the polymer is free of amonounsaturated monomer.